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From chunhui-shi <...@git.apache.org>
Subject [GitHub] drill pull request: DRILL-4237 DRILL-4478 fully implement hash to ...
Date Wed, 23 Mar 2016 17:36:29 GMT
Github user chunhui-shi commented on a diff in the pull request:

    https://github.com/apache/drill/pull/430#discussion_r57203072
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/MurmurHash3.java
---
    @@ -0,0 +1,264 @@
    +/**
    + * Licensed to the Apache Software Foundation (ASF) under one
    + * or more contributor license agreements.  See the NOTICE file
    + * distributed with this work for additional information
    + * regarding copyright ownership.  The ASF licenses this file
    + * to you under the Apache License, Version 2.0 (the
    + * "License"); you may not use this file except in compliance
    + * with the License.  You may obtain a copy of the License at
    + *
    + * http://www.apache.org/licenses/LICENSE-2.0
    + *
    + * Unless required by applicable law or agreed to in writing, software
    + * distributed under the License is distributed on an "AS IS" BASIS,
    + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    + * See the License for the specific language governing permissions and
    + * limitations under the License.
    + */
    +
    +
    +
    +package org.apache.drill.exec.expr.fn.impl;
    +
    +import io.netty.buffer.DrillBuf;
    +import io.netty.util.internal.PlatformDependent;
    +
    +
    +/**
    + *
    + * MurmurHash3 was written by Austin Appleby, and is placed in the public
    + * domain.
    + * See http://smhasher.googlecode.com/svn/trunk/MurmurHash3.cpp
    + * MurmurHash3_x64_128
    + * MurmurHash3_x86_32
    + */
    +public final class MurmurHash3 extends DrillHash{
    +
    +  public final class LongPair {
    +    public long val1;
    +    public long val2;
    +  }
    +
    +  public static final long fmix64(long k) {
    +    k ^= k >>> 33;
    +    k *= 0xff51afd7ed558ccdL;
    +    k ^= k >>> 33;
    +    k *= 0xc4ceb9fe1a85ec53L;
    +    k ^= k >>> 33;
    +    return k;
    +  }
    +
    +
    +
    +  /*
    +  Take 64 bit of murmur3_128's output
    +   */
    +  public static long murmur3_64(long bStart, long bEnd, DrillBuf buffer, int seed) {
    +
    +    long h1 = seed & 0x00000000FFFFFFFFL;
    +    long h2 = seed & 0x00000000FFFFFFFFL;
    +
    +    final long c1 = 0x87c37b91114253d5L;
    +    final long c2 = 0x4cf5ad432745937fL;
    +    long start = buffer.memoryAddress() + bStart;
    +    long end = buffer.memoryAddress() + bEnd;
    +    long length = end - start;
    +    long roundedEnd = start + ( length & 0xFFFFFFF0);  // round down to 16 byte block
    +    for (long i=start; i<roundedEnd; i+=16) {
    +      long k1 = getLongLittleEndian(i);
    +      long k2 = getLongLittleEndian(i+8);
    +      k1 *= c1; k1  = Long.rotateLeft(k1,31); k1 *= c2; h1 ^= k1;
    +      h1 = Long.rotateLeft(h1,27); h1 += h2; h1 = h1*5+0x52dce729;
    +      k2 *= c2; k2  = Long.rotateLeft(k2,33); k2 *= c1; h2 ^= k2;
    +      h2 = Long.rotateLeft(h2,31); h2 += h1; h2 = h2*5+0x38495ab5;
    +    }
    +
    +    long k1 = 0;
    +    long k2 = 0;
    +
    +    // tail
    +    switch ((int)length & 15) {
    +      case 15: k2  = (PlatformDependent.getByte(roundedEnd+14) & 0xffL) <<
48;
    --- End diff --
    
    Yes, k2 = 0 is needed and used if it directly go to cases between 14 to 9.


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